Total parenteral nutrition attenuates cerulein-induced pancreatitis in rats

Animal Models: Challenges and Opportunities to Determine Optimal Experimental Models of Pancreatitis and Pancreatic Cancer

At the 2018 PancreasFest meeting, experts participating in basic research met to discuss the plethora of available animal models for studying exocrine pancreatic disease. In particular, the discussion focused on the challenges currently facing the field and potential solutions. That meeting culminated in this review, which describes the advantages and limitations of both common and infrequently used models of exocrine pancreatic disease, namely, pancreatitis and exocrine pancreatic cancer. The objective is to provide a comprehensive description of the available models but also to provide investigators with guidance in the application of these models to investigate both environmental and genetic contributions to exocrine pancreatic disease. The content covers both nongenic and genetically engineered models across multiple species (large and small). Recommendations for choosing the appropriate model as well as how to conduct and present results are provided.

Effects of ω-3 fatty acids on toll-like receptor 4 and nuclear factor-κB p56 in lungs of rats with severe acute pancreatitis

AIM

To determine the effects of ω-3 fatty acids (ω-3FA) on the toll-like receptor 4 (TLR4)/nuclear factor κB p56 (NF-κBp56) signal pathway in the lungs of rats with severe acute pancreatitis (SAP).

METHODS

A total of 56 Sprague-Dawley rats were randomly divided into 4 groups: control group, SAP-saline group, SAP-soybean oil group and SAP-ω-3FA group. SAP was induced by the retrograde infusion of sodium taurocholate into the pancreatic duct. The expression of TLR4 and NF-κBp56 in the lungs was evaluated by immunohistochemistry and Western blot analysis. The levels of inflammatory cytokines interleukin-6 and tumor necrosis factor-alpha in the lungs were measured by enzyme-linked immunosorbent assay.

RESULTS

The expression of TLR4 and NF-κBp56 in lungs and of inflammatory cytokines in serum significantly increased in the SAP group compared with the control group (P < 0.05), but was significantly decreased in the ω-3FA group compared with the soybean oil group at 12 and 24 h (P < 0.05).

CONCLUSION

During the initial stage of SAP, ω-3FA can efficiently lower the inflammatory response and reduce lung injury by triggering the TLR4/NF-κBp56 signal pathway.

Potential influence of intravenous lipids on the outcomes of acute pancreatitis

Parenteral nutrition (PN) has been associated with a higher rate of adverse outcomes compared with enteral feeding in patients with acute pancreatitis (AP). However, PN may be necessary when feeding via the enteral route is poorly tolerated or impossible, and PN is recommended as a second-line nutrition therapy in AP. Intravenous (IV) lipids are commonly used as a part of PN in patients with AP. While the adverse outcomes related to the use of PN in AP have commonly been attributed to infectious complications, data suggest that the unsaturated fatty acids in the triglycerides used in IV lipids may contribute to the development of organ failure. We discuss the clinical and experimental data on this issue and the alternative lipid emulsions that are being studied.

Heat shock proteins and autophagy in rats with cerulein-induced acute pancreatitis

Background/Aims

Heat shock proteins (HSPs) protect rats from cerulein-induced acute pancreatitis (AP) by preventing the subcellular redistribution of cathepsin B and the activation of trypsinogen. Autophagy plays a critical role in the secretion of digestive enzymes and triggering of cerulein-induced AP via the colocalization of trypsinogen and lysosomes. Therefore, using a rat cerulein-induced AP model, we investigated whether HSPs prevent AP by regulating autophagy.

Methods

Twelve hours after fed standard laboratory chow and water, the experimental groups (cerulein, water-immersion [WI]-cerulein and heat-shock [HS]-cerulein) and the control groups (control, WI, and HS) received one intraperitoneal injection of cerulein (50 µg/kg) or saline, respectively. All of the rats were sacrificed at 6 hours after injection. The severity of the AP was assessed based on the serum amylase level and the histological and electron microscopy findings. Western blotting was also performed for HSP60/70 and LC3B-II.

Results

WI and HS induced HSP60 and HSP70, respectively. The induced HSP60/70 effectively prevented the development of cerulein-induced AP. Autophagy developed in the rats with cerulein-induced AP and was documented by the expression of LC3-II and electron microscopy findings. The WI-stressed rats and HS-treated rats did not develop cerulein-induced autophagy.

Conclusions

HSPs exert protective effects against cerulein-induced AP in rats by inhibiting autophagy.

Intravenous or luminal amino acids are insufficient to maintain pancreatic growth and digestive enzyme expression in the absence of intact dietary protein

We previously reported that rats receiving total parenteral nutrition (TPN) undergo significant pancreatic atrophy characterized by reduced total protein and digestive enzyme expression due to a lack of intestinal stimulation by nutrients (Baumler MD, Nelson DW, Ney DM, Groblewski GE. Am J Physiol Gastrointest Liver Physiol 292: G857-G866, 2007). Essentially identical results were recently reported in mice fed protein-free diets (Crozier SJ, D'Alecy LG, Ernst SA, Ginsburg LE, Williams JA. Gastroenterology 137: 1093-1101, 2009), provoking the question of whether reductions in pancreatic protein and digestive enzyme expression could be prevented by providing amino acids orally or by intravenous (IV) infusion while maintaining intestinal stimulation with fat and carbohydrate. Controlled studies were conducted in rats with IV catheters including orally fed/saline infusion or TPN-fed control rats compared with rats fed a protein-free diet, oral amino acid, or IV amino acid feeding, all with oral carbohydrate and fat. Interestingly, neither oral nor IV amino acids were sufficient to prevent the pancreatic atrophy seen for TPN controls or protein-free diets. Oral and IV amino acids partially attenuated the 75-90% reductions in pancreatic amylase and trypsinogen expression; however, values remained 50% lower than orally fed control rats. Lipase expression was more modestly reduced by a lack of dietary protein but did respond to IV amino acids. In comparison, chymotrypsinogen expression was induced nearly twofold in TPN animals but was not altered in other experimental groups compared with oral control animals. In contrast to pancreas, protein-free diets had no detectable effects on jejunal mucosal villus height, total mass, protein, DNA, or sucrase activity. These data underscore that, in the rat, intact dietary protein is essential in maintaining pancreatic growth and digestive enzyme adaptation but has surprisingly little effect on small intestinal mucosa.